Fundamental to using utilities for clinical decision making or cost-effectiveness analysis is the assumption hat utilities are stable over time. Yet, differences in observed vs. stated preferences and differences in references over time, called preference shifts or preference instability, have been noted. Preference (instability has been explored as a violation of the basic underpinnings of utility theory. Theorists have explored many reasons for this phenomenon such as differences in hypothetical vs. experienced health states, incomplete preferences at initial elicitation, and framing or labeling effects, to name a few. However, one major factor not previously explored that may be significantly associated with what appears as preference instability may be spouse/partner influence on health care decision making. There is considerable literature indicating that spouses, particularly female spouses/partners, may play a significant role in family health decisions. There is also evidence that female partners tend to show a preference for more aggressive therapies than male partners, regardless of outcome. The purpose of this study is to provide pilot data for an IROI to evaluate differences in preferences between men participating in a prostate cancer screening program and their spouses/partners, and to evaluate shifts in men's preference when responses are elicited with input from the female spouse/partner. Using the Time Trade-off technique, partners will be interviewed separately, then jointly, to determine their preferences, and potential shifts in preferences, for prostate cancel screening and treatment options. Based on our pilot data, we hypothesize that husband-wife/partner dyads will express significantly different preferences for prostate cancer-screening and therapies, with the wife's utility scores being higher for more aggressive options than their husband's. We further hypothesize that Husbands may initially state a preference for preserving quality of life at the risk of sacrificing life years, but hen the influence of the wife/partner is accounted for, the husband's preferences will shift to be more concordant with his wife's. This study builds on our previous extensive work in decision-making by testing the theoretical assumption regarding preference stability. The findings of the proposed study will have relevance to outcomes research and will also have application to clinical decision making.